This invention relates to multiple phase switching regulators. More particularly, this invention relates to multiple phase switching regulators with stage shedding.
A switching regulator is a power supply circuit that provides an output current to a load at a predetermined output voltage from an input voltage. Switching regulators can be designed to be highly efficient over a moderate range of load currents. Microprocessors have a broad range of current demand from very high peak currents to relatively low quiescent currents. Increasingly, microprocessors are requiring higher maximum output currents from switching regulators, which are continuing to operate over a wide output current dynamic range. As the range of output currents requirements expands, it becomes increasingly difficult to design a switching regulator that is efficient over a broad range of output currents.
Previously known multiple phase switching regulators include a plurality of switching regulators that are coupled in parallel to deliver high output currents to a load such as a microprocessor. A multiple phase switching regulator is an energy efficient DC/DC converter for supplying high output currents. The corresponding switching transistors in each switching regulator stage may be switched so that input current flows into only one regulator stage at a time. This technique reduces the amplitude of the output ripple current, input ripple current, and output ripple voltage.
However, previously known multiple phase switching regulators have poor efficiency at low output currents. Poor efficiency is due to the fact that the power required to turn the switching transistors ON and OFF becomes larger relative to the total power output of the regulator at low output currents.
One previously known single phase switching regulator circuit described in U.S. Pat. No. 5,481,178 discloses a technique called sleep mode for increasing efficiency in a switching regulator circuit at low load currents by not operating the switching transistors when the output capacitor is capable of maintaining the output voltage.
It would, therefore, be desirable to provide a multiple phase switching regulator that provides high efficiency over a broad range of load currents, including light load currents.
It would also be desirable to provide a multiple phase switching regulator that has a small amplitude output ripple current and output ripple voltage.
It would also be desirable to provide a multiple phase switching regulator that has a small amplitude input ripple current.
It is an object of the present invention to provide a multiple phase switching regulator that provides high efficiency over a broad range of load currents, including light load currents.
It is also an object of the present invention to provide a multiple phase switching regulator that has a small amplitude output ripple current and output ripple voltage.
It is also an object of the present invention to provide a multiple phase switching regulator that has a small amplitude input ripple current.
The present invention provides a multiple phase switching regulator with stage shedding that provides high efficiency at light load currents. The present invention also includes methods for providing high efficiency in a multiple phase switching regulator circuit using stage shedding. Multiple phase switching regulators of the present invention include a plurality of single phase switching regulator circuits coupled in parallel to an output capacitor. At high and moderate load currents, each single phase switching regulator circuit supplies output current to the load. When the load current falls below a first threshold, stage shedding is implemented during which one or more of the single phase switching regulator circuits are OFF during a first low power mode to increase efficiency. At least one single phase switching regulator circuit is maintained ON to supply output current in the first low power mode. The one or more single phase switching regulators that remain ON may increase their total output current to supply the load current.
Multiple phase switching regulators of the present invention may have any number N of low power modes. For example, one or more additional single phase switching regulators may be OFF in a second low power mode after the first low power mode has commenced. The second low power mode commences after the load current drops below a second threshold lower than the first threshold. The output current of the switching regulators that remain ON in the second low power mode increase their total output current to supply the load current. Multiple phase switching regulators of the present invention provide a low amplitude output ripple current, input ripple current, and output ripple voltage at light load currents.